1. Field of the Invention
The present invention relates to an integrated-inverter electric compressor for an in-vehicle air-conditioning apparatus, the compressor being formed by integrating an inverter with the outer periphery of a housing accommodating electric motor and a compressor.
This application is based on Japanese Patent Application No. 2008-88598, the content of which is incorporated herein by reference.
2. Description of Related Art
Recently, various electric compressors having integrated inverters have been proposed for in-vehicle air-conditioning apparatuses. These integrated-inverter electric compressors have an inverter container (inverter box) on the outer circumference of a housing accommodating an electric motor and a compressor, and an inverter device, provided inside the inverter container, that converts DC power supplied from a high-voltage power supply unit to three-phase AC power and supplies it to the electric motor via a glass sealed terminal. In this way, the rotational speed of the compressor is variably controlled according to the air-conditioning load.
As described in Japanese Unexamined Patent Application, Publication No. 2004-162618, the inverter is integrated with the outer circumferential section of the compressor housing by providing a power-related substrate (including a pedestal and unit base) a control-related substrate (printed circuit board) in two vertical layers. The power-related substrate has a plurality of power semiconductor switching devices (IGBT) for converting DC power to three-phase AC power. The control-related substrate has a control and communication circuit having a device, such as a CPU, that operates at low voltage. The substrates are mounted to the outer circumferential section of the compressor housing by accommodating them inside an inverter case or an external frame.
Japanese Unexamined Patent Application, Publication No. HEI-7-304327 describes an air conditioner, for electric vehicles, which is capable of eliminating electromagnetic-wave interference by using shielded lines as power-supply lines, which supply DC power to an electric compressor driving device (inverter device) and three-phase lines which supply three-phase electric power from the electric compressor driving device to a motor, and by grounding the shield to a metal case for the components, including the electric compressor driving device, via a capacitor.
However, with an integrated-inverter electric compressor in which an inverter device, which includes a power-related substrate and a control-related substrate, is integrated with a housing, such as that described in Japanese Unexamined Patent Application, Publication No. 2004-162618, both substrates are frame-grounded separately. Therefore, the grounding structure is complicated, and to reduce the size of the inverter device, there are problems in how to frame-ground noise currents, such as electromagnetic noise generated at the power-related substrate due to the switching operation of the IGBT etc., and electromagnetic noise transmitted from the outside to the control-related substrate via a communication line, to the housing of the electric compressor in order to reduce noise interference and noise leaking to the outside.
In other words, when reducing the size of the inverter device, one problem is how to simplify the grounding structure from the power-related substrate and the control-related substrate to the electric compressor housing. Another problem is how to ground the power-related substrate and the control-related substrate to the electric compressor housing. Although Japanese Unexamined Patent Application, Publication No. HEI-7-304327 describes the metal case for components, including an electric compressor driving device, it does not describe any specific grounding structure.